Surfactant composition

ABSTRACT

A surfactant composition contains at least one sorbitan ester and at least one sorbitol ester wherein the mean number of carbon atoms of the hydrophobe of the sorbitan ester is greater than that of the sorbitol ester. The surfactant composition is particularly suitable for use in stabilizing emulsions, especially personal care or cosmetic products.

CROSS REFERENCE TO RELATED APPLICATION

This application is the National Phase application of InternationalApplication No. PCT/GB2005/001389, filed Apr. 23, 2005, which designatesthe United States and was published in English. This application, in itsentirety, is incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to a surfactant composition comprising asorbitan-ester and a sorbitol ester, to an emulsion formed using thesurfactant composition, and in particular to a personal care or cosmeticproduct formed from the emulsion.

BACKGROUND

Sorbitan esters have been used for many years as surface active agents,having emulsifying, dispersing, wetting and/or solubilising propertiesin a wide range of applications such as personal care, cleaning, generalindustrial, food, and many others. In particular, sorbitan esters havebeen used as emulsifiers in personal care applications, for example skincare, sunscreens, toiletries, decorative cosmetics, perfumes andfragrances.

Commercial production of sorbitan esters normally involves the reactionof sorbitol with fatty acids or derivatives thereof, and results in acomplex mixture of products including sorbitol mono- di-, tri-, andhigher esters, sorbitan mono-, di-, and higher-esters, isosorbide mono-,and di-esters, and non-esterified sorbitol, sorbitan and isosorbide. Theconcentrations of the aforementioned individual components can vary, butsorbitan esters are the main components. There can be significantamounts of isosorbide esters present, but sorbitol esters are normallypresent at very low concentrations. The number of carbon atoms presentin the hydrophobe of the sorbitol/sorbitan/isosorbide esters isdependant upon the particular fatty acid(s) employed in the reaction,and the average number thereof will be substantially the same for all ofthe components.

Current commercially available sorbitan esters are effective emulsifiersin many applications, but there is still a requirement to improve theproperties thereof, particularly in personal care applications, such asflexibility of use, improved water resistance, smooth and light skinfeel, and spreading properties. Often an additional co-emulsifier isrequired to be used with sorbitan esters, and there would be significantadvantages if a sorbitol based self-emulsifying system could bedeveloped, i.e. without the need for a co-emulsifier, particularly onecapable of forming liquid crystals in water, and especially in oil inwater emulsions.

SUMMARY OF THE INVENTION

We have now surprisingly discovered a surfactant composition whichovercomes or significantly reduces at least one of the aforementionedproblems.

Accordingly, the present invention provides a surfactant compositioncomprising at least one sorbitan ester and at least one sorbitol esterwherein the mean number of carbon atoms of the hydrophobe of thesorbitan ester is greater than that of the sorbitol ester.

The invention also provides a method of forming a surfactant compositionwhich comprises mixing together a sorbitan ester component and asorbitol ester component wherein the mean number of carbon atoms of thehydrophobe of the sorbitan ester is greater than that of the sorbitolester.

The invention further provides an emulsion comprising a surfactantcomposition capable of forming liquid crystals in water which comprisesat least one sorbitan ester and at least one sorbitol ester wherein themean number of carbon atoms of the hydrophobe of the sorbitan ester isgreater than that of the sorbitol ester.

The invention further provides a personal care or cosmetic productcomprising a surfactant composition comprising at least one sorbitanester and at least one sorbitol ester wherein the mean number of carbonatoms of the hydrophobe of the sorbitan ester is greater than that ofthe sorbitol ester.

The invention still further provides the use of a surfactant compositioncomprising at least one sorbitan ester and at least one sorbitol esterwherein the mean number of carbon atoms of the hydrophobe of thesorbitan ester is greater than that of the sorbitol ester, to stabilisean emulsion.

The invention yet further provides the use of a surfactant compositioncomprising at least 3% by weight of at least one sorbitol ester, to formliquid crystals in the water phase of an oil in water emulsion, tostabilise the emulsion.

The sorbitan and/or sorbitol esters used in the present invention arenormally made by reacting sorbitol with fatty acids or derivativesthereof, e.g. fatty acid methyl, ethyl and/or isopropyl esters, or fattyacid triglycerides. Preferred fatty acids comprise in the range from 8to 24, more preferably 10 to 22, particularly 12 to 20, and especially12 to 18 carbon atoms. Linear fatty acids are preferred. Suitable fattyacids include capric, lauric, myristic, palmitic, stearic, and/orbehenic acid.

In a preferred embodiment greater than 80%, more preferably greater than85%, particularly greater than 90%, and especially greater than 95% byweight of saturated fatty acids are employed. The concentration ofunsaturated fatty acids used is preferably less than 20%, morepreferably less 15%, particularly less than 10%, and especially lessthan 5% by weight. Oleic acid is a particularly suitable unsaturatedfatty acid.

The mean number of carbon atoms (on a molar basis) present in thehydrophobe (derived from the fatty acid or derivative thereof) of thesorbitan esters is suitably at least 1, preferably at least 2, morepreferably in the range from 3 to 7, particularly 4 to 6, and especially4.5 to 5 greater than the mean number of carbon atoms present in thehydrophobe of the sorbitol esters. The mean number of carbon atoms ofthe sorbitan ester hydrophobe is suitably in the range from 12 to 24,preferably 14 to 20, more preferably 15 to 19, particularly 16 to 18,and especially 16.5 to 17.5. The mean number of carbon atoms of thesorbitol ester hydrophobe is suitably in the range from 8 to 20,preferably 10 to 16, more preferably 11 to 14, particularly 11.5 to 13,and especially 12 to 12.5.

The ratio of sorbitan esters to sorbitol esters present in a compositionaccording to the present invention is suitably in the range from 1 to50:1, preferably 2 to 30:1, more preferably 4 to 20:1, particularly 7 to13:1, and especially 9 to 11:1 by weight.

The concentration of sorbitan esters is suitably in the range from 25 to95%, preferably 45 to 90%, more preferably 60 to 85%, particularly 65 to80%, and especially 69 to 73% by weight of the total composition. Theconcentration of sorbitol esters is suitably in the range from 1 to 25%,preferably 3 to 15%, more preferably 5 to 12%, particularly 7 to 9%, andespecially 7.5 to 8.5% by weight of the total composition. Theconcentration of isosorbide esters is suitably in the range from 3 to35%, preferably 7 to 25%, more preferably 10 to 20%, particularly 14 to18%, and especially 15 to 17% by weight of the total composition.

Suitable sorbitan esters include sorbitan cocoate, sorbitan caprate,sorbitan laurate, sorbitan myristate, sorbitan palmitate and/or sorbitanstearate. Preferred sorbitan esters are sorbitan palmitate and/orsorbitan stearate.

In a particularly preferred embodiment, the concentration of sorbitanpalmitate and/or sorbitan stearate is at least 70%, more preferably atleast 90%, particularly at least 95%, and especially at least 98% byweight of the total concentration of sorbitan esters present in thecomposition. When present as a mixture, the molar ratio of sorbitanpalmitate to sorbitan stearate is preferably in the range from 0.3 to4:1, more preferably 0.5 to 2:1, particularly 0.7 to 1.5:1, andespecially 0.9 to 1.1:1.

A preferred minor sorbitan ester component is sorbitan laurate which ispreferably present at a concentration of less than 5%, more preferablyless than 3%, particularly in the range from 0.2 to 2%, and especially0.5 to 1.5% by weight of the total concentration of sorbitan esters.

The sorbitan esters used in the present invention preferably comprise amixture of mono-, di-, tri-, and optionally tetra-, esters. Theconcentration of monoesters is suitably at least 20%, preferably atleast 25%, more preferably at least 30%, particularly at least 35%, andespecially at least 40% by weight based upon the total concentration ofsorbitan esters. The concentration of the combination of monoesters anddiesters is suitably at least 50%, preferably at least 65%, morepreferably at least 75%, particularly at least 80%, and especially atleast 85% by weight based upon the total concentration of sorbitanesters. Correspondingly, the concentration of tri- and tetra-esters issuitably not more than 50%, preferably not more than 35%, morepreferably not more than 25%, particularly not more than 20%, andespecially not more than 15% by weight based upon the totalconcentration of sorbitan esters.

Suitable sorbitol esters include sorbitol cocoate, sorbitol caprate,sorbitol laurate, sorbitol myristate, sorbitol palmitate and/or sorbitolstearate, preferably sorbitol laurate, sorbitol palmitate and/orsorbitol stearate, and more preferably sorbitol laurate.

In a preferred embodiment, the concentration of sorbitol laurate issuitably in the range from 0.5 to 25%, preferably 2 to 15%, morepreferably 4 to 10%, particularly 6 to 8%, and especially 6.5 to 7.5% byweight of the total composition. In addition, the concentration ofsorbitol laurate is suitably at least 30%, preferably at least 50%, morepreferably at least 70%, particularly at least 80%, and especially atleast 90% by weight of the total concentration of sorbitol esterspresent in the composition. Further, the concentration of sorbitollaurate is preferably at least 1, more preferably at least 5,particularly at least 7, and especially at least 10 times by weightgreater than any other individual sorbitol ester present in thecomposition. Thus, sorbitol laurate is preferably the predominantsorbitol ester present in the composition.

Preferred minor sorbitol esters are sorbitol palmitate and/or sorbitolstearate, suitably present at a combined concentration of less than 7%,preferably less than 5%, more preferably less than 3%, particularly lessthan 1%, and especially less than 0.5% by weight of the totalcomposition.

The sorbitol esters used in the present invention preferably comprise amixture of mono- and di-esters. The concentration of monoesters issuitably at least 40%, preferably at least 60%, more preferably at least70%, particularly at least 80%, and especially at least 85% by weightbased upon the total concentration of sorbitol esters. The concentrationof diesters is suitably less than 60%, preferably less than 40%, morepreferably less than 30%, particularly less than 20%, and especiallyless than 15% by weight based upon the total concentration of sorbitolesters.

The concentration of free polyol, preferably sorbitol, sorbitan and/orisosorbide, present in a composition according to the present inventionis suitably in the range from 0.5 to 20%, preferably 2 to 15%, morepreferably 3 to 10%, particularly 4.5 to 6%, and particularly 5 to 5.5%by weight of the total composition. Suitably greater than 20%,preferably in the range from 30 to 80%, more preferably 35 to 70%,particularly 40 to 60%, and especially 45 to 55% by weight of the freepolyol is sorbitol.

The surfactant composition according to the present invention ispreferably formed by mixing together (i) a composition predominantlycomprising sorbitan ester (hereinafter referred to as the sorbitan estercomponent), and (ii) a composition predominantly comprising sorbitolester (hereinafter referred to as the sorbitol ester component).

The sorbitan ester component suitably comprises sorbitan ester at aconcentration in the range from 25 to 98%, preferably 45 to 90%, morepreferably 65 to 85%, particularly 74 to 82%, and especially 76 to 80%by weight of the total composition.

Suitable sorbitan esters include sorbitan cocoate, sorbitan caprate,sorbitan laurate, sorbitan myristate, sorbitan palmitate and/or sorbitanstearate. Preferred sorbitan esters are sorbitan palmitate and/orsorbitan stearate.

The concentration of sorbitan palmitate and/or sorbitan stearate ispreferably at least 75%, more preferably at least 92%, particularly atleast 97%, and especially at least 99% by weight of the totalconcentration of sorbitan esters present in the sorbitan estercomponent. The preferred molar ratios, when present as a mixture, ofsorbitan palmitate to sorbitan stearate in the sorbitan ester componentare the same as those given above for the surfactant compositionaccording to the present invention.

The preferred concentration ranges of sorbitan monoesters, diesters, andhigher esters in the sorbitan ester component are the same as thosegiven above for the surfactant composition according to the presentinvention.

The concentration of sorbitol ester in the sorbitan ester component issuitably less than 10%, preferably less than 6%, more preferably lessthan 3%, particularly less than 1%, and especially less than 0.5% byweight of the total composition. The sorbitol ester suitably comprisessorbitol palmitate and/or sorbitol stearate, preferably present at amolar ratio in the range from 0.3 to 4:1, more preferably 0.5 to 2:1,particularly 0.7 to 1.5:1, and especially 0.9 to 1.1:1.

The concentration of isosorbide esters in the sorbitan ester componentis suitably in the range from 3 to 40%, preferably 8 to 30%, morepreferably 12 to 25%, particularly 16 to 20%, and especially 17 to 19%by weight of the total composition.

The concentration of free polyol, preferably sorbitol, sorbitan and/orisosorbide, present in the sorbitan ester component is suitably in therange from 0.5 to 15%, preferably 1 to 10%, more preferably 1.5 to 6%,particularly 2 to 4%, and particularly 2.5 to 3.5% by weight. Preferablygreater than 30%, more preferably in the range from 50 to 95%,particularly 60 to 85%, and especially 70 to 80% by weight of the freepolyol is sorbitan.

The sorbitan ester component suitably has a HLB value in the range from3 to 10, preferably 3.5 to 8, more preferably 4 to 6, particularly 4.4to 5, and especially 4.6 to 4.8.

The concentration of sorbitol ester in the sorbitol ester component issuitably at least 25%, preferably in the range from 40 to 95%, morepreferably 50 to 85%, particularly 60 to 80%, and especially 65 to 75%by weight of the total composition.

Suitable sorbitol esters include sorbitol cocoate, sorbitol caprate,sorbitol laurate, sorbitol myristate, sorbitol palmitate and/or sorbitolstearate, and preferably sorbitol laurate.

The concentration of sorbitol laurate is preferably at least 50%, morepreferably at least 80%, particularly at least 90%, and especially atleast 95% by weight of the total amount of sorbitol esters present inthe sorbitol ester component.

The concentration of sorbitan ester, preferably sorbitan laurate, in thesorbitol ester component is suitably less than 30%, preferably in therange from 1 to 20%, more preferably 3 to 12%, particularly 5 to 9%, andespecially 6 to 8% by weight of the total composition.

The concentration of free polyol, preferably sorbitol, sorbitan and/orisosorbide, present in the sorbitol ester component is preferably in therange from 2 to 60%, more preferably 10 to 50%, particularly 15 to 40%,and particularly 20 to 30% by weight of the total composition.Preferably greater than 50%, more preferably greater than 75%,particularly greater than 85%, and especially greater than 95% by weightof the free polyol in the sorbitol ester component is sorbitol.

The preferred concentration ranges of sorbitol monoesters and diestersin the sorbitol ester component are the same as those given above forthe surfactant composition according to the present invention.

In order to form a surfactant composition according to the presentinvention, the sorbitan ester component is suitably mixed together withthe sorbitol ester component at a weight ratio in the range from 0.5 to100:1, preferably 3 to 50:1, more preferably 7 to 15:1, particularly 8to 10:1, and especially 8.5 to 9.5:1.

The surfactant composition according to the present invention is capableof forming liquid crystals in water, preferably forms liquid crystals,more preferably in emulsions, and particularly in oil in wateremulsions. The liquid crystals which are formed are preferably lyotropicliquid crystals (i.e. both concentration and temperature dependant),more preferably lamellar phase liquid crystals, and particularly L alphaphase (neat) liquid crystals.

The surfactant composition is suitable for use in forming emulsions (anddispersions), i.e. as the, or as part of the, emulsifier system, such aswater in oil emulsions, oil in polyol (e.g. glycerol) emulsions,particularly oil in water emulsions, and especially for use in personalcare or cosmetic products.

The oil phase of the emulsion according to the present invention willpreferably mainly be an emollient oil of the type used in personal careor cosmetic products. The emollient can and usually will be an oilymaterial which is liquid at ambient temperature. Alternatively it can besolid at ambient temperature, in which case in bulk it will usually be awaxy solid, provided it is liquid at an elevated temperature at which itcan be included in and emulsified in the composition. The manufacture ofthe composition preferably uses temperatures up to 100° C., morepreferably about 80° C., and therefore such solid emollients willpreferably have melting temperatures of less than 100° C., and morepreferably less than 70° C.

Suitable normally liquid emollient oils include non-polar oils, forexample mineral or paraffin, especially isoparaffin, oils, such as thatsold by Uniqema as Arlamol (trade mark) HD; or medium polarity oils, forexample vegetable ester oils such as jojoba oil, vegetable glycerideoils, animal glyceride oils, such as that sold by Uniqema as Estol(trade mark) 3603 (caprylic/capric triglyceride), synthetic oils, forexample synthetic ester oils, such as isopropyl palmitate and those soldby Uniqema as Estol 1512 and Arlamol DOA, ether oils, particularly oftwo fatty e.g. C8 to C18 alkyl residues, such as that sold by Cognis asCetiol OE (dicaprylether), guerbet alcohols such as that sold by Cognisas Eutanol G (octyl dodecanol), or silicone oils, such as dimethicioneoil such as those sold by Dow Corning as DC200, cyclomethicone oil, orsilicones having polyoxyalkylene side chains to improve theirhydrophilicity; or highly polar oils including alkoxylate emollients forexample fatty alcohol propoxylates such as that sold by Uniqema asArlamol E (propoxylated stearyl alcohol). Suitable emollient materialsthat can be solid at ambient temperature but liquid at temperaturestypically used to make the compositions of this invention include jojobawax, tallow and coconut wax/oil. When non-polar oils are used it may bedesirable to use relatively high concentrations of surfactantcomposition according to the present invention, in order to achievesuitably satisfactory emulsification, particularly to obtain small oildroplets.

Mixtures of emollients can and often will be used, and in some casessolid emollients may dissolve wholly or partly in liquid emollients orin combination the freezing point of the mixture is suitably low. Wherethe emollient composition is a solid (such as fatty alcohols) at ambienttemperature, the resulting dispersion may technically not be an emulsion(although in most cases the precise phase of the oily disperse phasecannot readily be determined) but such dispersions behave as if theywere true emulsions and the term emulsion is used herein to include suchcompositions.

The concentration of the oil phase may vary widely. The amount of oil inthe emulsion is suitably in the range from 1 to 90%, preferably 3 to60%, more preferably 5 to 40%, particularly 8 to 20%, and especially 10to 15% by weight of the total composition.

The amount of water (or polyol, e.g. glycerin) present in the emulsionis suitably greater than 5%, preferably in the range from 30 to 90%,more preferably 50 to 90%, particularly 70 to 85%, and especially 75 to80% by weight of the total composition. The amount of surfactantcomposition defined herein in an emulsion or personal care or cosmeticproduct according to the present invention is suitably in the range from0.1 to 10%, preferably 0.5 to 8%, more preferably 1 to 7%, particularly1.5 to 6%, and especially 2 to 5.5%, by weight of the total composition.

The emulsions according to the present invention may also contain otheradditional surfactant materials which form part of the emulsifiersystem. Other suitable surfactants include relatively hydrophilicsurfactants, e.g. having a HLB value of greater than 10, preferablygreater than 12, and relatively hydrophobic surfactants e.g. having aHLB value of less than 10, preferably less than 8. Relativelyhydrophilic surfactants include alkoxylate surfactants with an averagein the range from about 10 to about 100 alkylene oxide, particularlyethylene oxide residues; and relatively hydrophobic surfactants includealkoxylate surfactants preferably with an average in the range fromabout 3 to about 10 alkylene oxide, particularly ethylene oxideresidues.

Personal care or cosmetic emulsions can be divided by viscosity intomilks and lotions, which preferably have a low shear viscosity (measuredat shear rates of about 0.1 to 10 s⁻¹ as is typically used in Brookfieldviscometers) of up to 10,000 mPa·s, and creams which preferably have alow shear viscosity of more than 10,000 mPa·s. Milks and lotionspreferably have a low shear viscosity in the range from 100 to 10,000,more preferably 200 to 5,000, and particularly 300 to 1,000 mPa·s. Theamount of surfactant composition according to the present inventionpresent in a milk or lotion is preferably in the range from 2 to 3% byweight of the total composition.

Creams preferably have a low shear viscosity of at least 20,000, morepreferably in the range from 30,000 to 80,000, and particularly 40,000to 70,000 mPa·s, although even higher viscosities e.g. up to about 10⁶mPa·s, may also be used. The amount of surfactant composition present ina cream is preferably in the range from 4 to 5.5% by weight of the totalcomposition.

The emulsions of the invention may be made by generally conventionalemulsification and mixing methods. For example, the surfactantcomposition may be added to (i) the oil phase, which is then added tothe aqueous phase, or (ii) both the combined oil and water phases, or(iii) the water phase, which is then added to the oil phase. Method(iii) is preferred. In all of these methods, the resulting mixture canthen be emulsified using standard techniques. It is preferred to eitherheat the aqueous and oil phases usually above about 60° C., e.g. toabout 80 to 85° C., or to subject the aqueous phase to high intensitymixing at lower, e.g. about ambient, temperature. Vigorous mixing andthe use of moderately elevated temperatures can be combined if desired.The heating and/or high intensity mixing can be carried out before,during or after addition of the oil phase but once emulsified, careshould be taken not to destroy the liquid crystal system by excessivemixing or stirring.

The emulsions can also be made by inverse emulsification methods,whereby the surfactant composition is added to either the oil phase orthe aqueous phase, and the aqueous phase is mixed into the oil phase toinitially form a water in oil emulsion. Aqueous phase addition iscontinued until the system inverts to form an oil in water emulsion.Plainly a substantial amount of aqueous phase will generally be neededto effect inversion and so this method is not likely to be used for highoil phase content emulsions. Vigorous mixing and the use of moderatelyelevated temperatures can be combined if desired. Heating can be carriedout during or after addition of the aqueous phase and before, during orafter inversion. High intensity mixing can be carried out during orafter addition of the aqueous phase, and before or during inversion

The emulsions may for example be microemulsions or nanoemulsions, havinga mean droplet size over a wide range, preferably in the range from 10to 10,000 nm. In one embodiment, the emulsion droplet size may bereduced, for example by high pressure homogenisation, preferably to avalue in the range from 100 to 1,000 nm, more preferably 300 to 600 nm.

The emulsions according to the present invention are stable, measured asdescribed herein, preferably for greater than one month, more preferablygreater than two months, particularly greater than three months, andespecially greater than four months at ambient temperature (23° C.), andalso preferably at 40° C. The stability at even higher temperatures canbe particularly important, and therefore the emulsion is stable,measured as described herein, suitably for greater than one week,preferably greater than two weeks, more preferably greater than 3 weeks,particularly greater than one month, and especially greater than twomonths at 50° C. In a particularly preferred embodiment, the liquidcrystals created during emulsion formation are substantially maintainedduring the aforementioned time and temperature testing regimes.

Many other components may be included in the emulsions to make personalcare or cosmetic compositions or products. These components can be oilsoluble, water soluble or non-soluble. Examples of such materialsinclude:

(i) preservatives such as those based on parabens (alkyl esters of4-hydroxybenzoic acid), phenoxyethanol, substituted ureas and hydantoinderivatives e.g. those sold commercially under the trade names GermabenII Nipaguard BPX and Nipaguard DMDMH, when used preferably at aconcentration in the range from 0.5 to 2% by weight of the totalcomposition;(ii) perfumes, when used preferably at a concentration in the range from0.1 to 10% more preferably up to about 5%, and particularly up to about2% by weight of the total composition;(iii) humectants or solvents such as alcohols, polyols such as glyceroland polyethylene glycols, when used preferably at a concentration in therange from 1 to 10% by weight of the total composition;(iv) sunfilter or sunscreen materials including organic sunscreensand/or inorganic sunscreens including those based on titanium dioxide orzinc oxide; when used preferably at a concentration in the range from0.1% to 20%, more preferably 1 to 15%, and particularly 2 to 10% byweight of the total composition;(v) alpha hydroxy acids such as glycolic, citric, lactic, malic,tartaric acids and their esters; self-tanning agents such asdihydroxyacetone;(vi) antimicrobial, particularly anti-acne components such as salicylicacid;(vii) vitamins and their precursors including: (a) Vitamin A, e.g. asretinyl palmitate and other tretinoin precursor molecules, (b) VitaminB, e.g. as panthenol and its derivatives, (c) Vitamin C, e.g. asascorbic acid and its derivatives, (d) Vitamin E, e.g. as tocopherylacetate, (e) Vitamin F, e.g. as polyunsaturated fatty acid esters suchas gamma-linolenic acid esters;(viii) skin care agents such as ceramides either as natural materials orfunctional mimics of natural ceramides;(ix) phospholipids, such as synthetic phospholipids or naturalphospholipids, eg lecithin;(x) vesicle-containing formulations;(xi) germanium-containing compounds for example that sold by Uniqema asArlamol GEO;(xii) botanical extracts with beneficial skin care properties;(xiii) skin whiteners such as Arlatone Dioic DCA (trade mark) sold byUniqema, kojic acid, arbutin and similar materials;(xiv) skin repair compounds actives such as Allantoin and similarseries;(xv) caffeine and similar compounds;(xvi) cooling additives such as menthol or camphor;(xvii) insect repellents such as N,N-diethyl-3-methylbenzamide (DEET)and citrus or eucalyptus oils;(xviii) essential oils;(xix) ethanol; and(xx) pigments, including microfine pigments, particularly oxides andsilicates, e.g. iron oxide, particularly coated iron oxides, and/ortitanium dioxide, and ceramic materials such as boron nitride, or othersolid components, such as are used in make up and cosmetics, to givesuspoemulsions, preferably used in an amount in the range from 1 to 15%,more preferably at least 5% and particularly approximately 10%.

The surfactant composition and emulsions according to the presentinvention are suitable for use in a wide range of compositions andend-use applications, such as moisturizers, sunscreens, after sunproducts, body butters, gel creams, high perfume containing products,perfume creams, baby care products, hair conditioners, skin toning andskin whitening products, water-free products, anti-perspirant anddeodorant products, tanning products, cleansers, 2-in-1 foamingemulsions, multiple emulsions, preservative free products, emulsifierfree products, mild formulations, scrub formulations e.g. containingsolid beads, silicone in water formulations, pigment containingproducts, sprayable emulsions, colour cosmetics, conditioners, showerproducts, foaming emulsions, make-up remover, eye make-up remover, andwipes.

Formulations containing a surfactant composition or emulsion accordingto the present invention may have a pH value over a wide range,preferably in the range from 3 to 13, more preferably 5 to 10, andespecially 6 to 8.

One preferred embodiment is as a sunscreen which contains one or moreorganic sunscreens and/or inorganic sunscreens such as metal oxides, butpreferably comprises at least one particulate titanium dioxide and/orzinc oxide, particularly included in the composition in the form of anaqueous and/or organic, preferably aqueous, dispersion availablecommercially from Uniqema under the trade marks Tioveil and SolaveilClarus (both titanium dioxide) and Spectraveil (zinc oxide). Inaddition, organic sunscreens may be used together with the preferredmetal oxide sunscreens, and include p-methoxy cinnamic acid esters,salicylic acid esters, p-amino benzoic acid esters, non-sulphonatedbenzophenone derivatives, derivatives of dibenzoyl methane and esters of2-cyanoacrylic acid. Specific examples of useful organic sunscreensinclude benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-6,benzophenone-8, benzophenone-12, isopropyl dibenzoyl methane, butylmethoxy dibenzoyl methane, ethyl dihydroxypropyl PABA, glyceryl PABA,octyl dimethyl PABA, octyl methoxycinnamate, homosalate, octylsalicylate, octyl triazone, octocrylene, etocrylene, menthylanthranilate, 4-methylbenzylidene camphor, benzophenone 4, and phenylbenzimidazole sulphonic acid.

End use sunscreen formulations containing the surfactant compositionaccording to the present invention can exhibit surprisingly improvedwater resistance and/or sun protection (SPF values).

In this specification the following test methods have been used.

(1) Analysis of C12 Sorbitol Esters by Reverse Phase HPLC

The test sample was dissolved in isopropyl alcohol/water and injected ona HPLC system using a Reversed Phase C8 column and an evaporative lightscattering detector. The different sorbitol esters and unreacted polyolwere eluted using a gradient of water and acetonitrile and indentifiedby their retention times. Quantification was based on peak area percent.

(a) Reagents

All reagents were of recognised analytical quality, namely isopropylalcohol, acetonitrile, and water (all ‘HiPerSolve’, ex BDH).

(b) Equipment

HPLC system employed was Agilent 1100 series comprising G1379Ade-gasser, G1311A quaternary pump, G1313A autosampler and G1316A columnoven with a Polymer Labs PL ELS-1000 evaporative light scatteringdetector and Chemstation LC software. Other materials used were 28.25 mlglass vial (ex VWR 215007823), 2 ml autosampler vial (ex VWR 372111102),11 mm autosampler vial crimp cap (ex VWR 372211134), 11 mm vial crimpingtool (VWR 372340544), disposable pasteur pipettes (ex VWR 241259352),Zorbax Eclipse XDB-C8 HPLC column, 5 μm, 150 mm length×4.6 mm internaldiameter (Part No 993967-906).

(c) Procedure

(i) Power to Agilent 1100 series HPLC system turned on.

(ii) Solvent reservoirs topped up, as required.

(iii) Power and nitrogen supply to the Polymer labs PL ELS-1000evaporative light scattering detector turned on.

(iv) Power to HPLC computer turned on.

(v) Software for PL ELS-1000 detector started.

(vi) The method employed had the following settings; evaporatortemperature=85° C., nebuliser temperature=60° C., gas flow rate=1.0liters/min, autozero offset=0, and time constant=0. The detector wasallowed to stabilize for 20 minutes prior to use.

(vii) Software for HPLC started up.

(viii) Method was set up according to the following parameters; eluent Awas water, eluent B was acetonitrile, gradient was as Table 1 below,flow=1.0 ml/min, injection volume=20 μl, column temperature=40° C., andrun time=40 minutes.

TABLE 1 Gradient Time (min) Water Acetonitrile 0 75% 25% 5  5% 90% 35 5% 90% 35.1 75% 25% 40 75% 25%(ix) Approximately 50±5 mg of sample was dissolved in 10 ml of isopropylalcohol. Gentle heating was used to speed up the dissolution process, ifrequired. If the sample was still not in solution, a few drops of waterwere added until the solution was clear.(x) Using a clean pasteur pipette, a 2 ml autosampler vial was filledwith the solution and the vial closed using a crimp cap and crimpingtool.(xi) Sample vial was placed in autosampler tray.(xii) Sample details were entered.(xiii) Sample was run.(d) Results

All peaks in the resultant chromatogram were integrated and summed. Peakareas for polyol, and the various ester peaks were then calculated andexpressed as a percentage of the total peak areas (polyol and estercomponent peaks were identified by LC-MS or by LC retention times ofstandards).

(2) Analysis of C16/C18 Sorbitan Esters by Reverse Phase HPLC

The procedure described in (1) above for sorbitol esters was employedexcept that (i) an Inertsil ODS-2 HPLC Column, 5 μm, 250 mm length×4.6mm internal diameter (Chrompack Cat. No. 28408) was used, (ii) acetonewas used instead of water, and (iii) the gradient was as in Table 2below.

TABLE 2 Gradient Time (min) Acetonitrile Acetone 0 90% 10% 25 10% 90% 3510% 90% 36 90% 10% 40 90% 10%(3) Emulsion Stability

Stability was assessed by observing the emulsions after storage atambient temperature (23° C.), cold at 5° C. or under elevatedtemperature storage at 40° C. and 50° C. Measuring storage stability at50° C. is a very severe test. The composition was stable if no visibleseparation of the emulsion occurred. The stability of the liquidcrystals in the emulsion was also assessed by observing under amicroscope using polarized light.

(4) Emulsion Viscosity

Viscosity was measured at 23° C. with a Brookfield LVT viscometer usingan appropriate spindle (LV1, LV2, LV3, or LV4—depending on the viscosityof the emulsion being tested) at 6 rpm (0.1 Hz), 1 day after making theemulsions and results are quoted in mPa·s.

The invention is illustrated by the following non-limiting examples.

EXAMPLES Example 1 (i) Preparation of Sorbitan Ester Component

400 g of a 1:1 molar mixture of palmitic and stearic acids, 290 g 70%aqueous sorbitol, 5 g 50% aqueous NaOH and 3 g 50% aqueous phosphorousacid were charged to a 1 liter flask, fitted with a stirrer, side-armdistillation, thermocouple, nitrogen sparge and a thermostatted electricmantle. The reaction mixture was heated with stirring to about 245° C.and water distilled off until the acid value was less than 10 mg KOH·g⁻¹and the OH value was less than 260 mg KOH·g⁻¹. The product was thencooled and discharged.

The product was analysed as described herein and comprised 78% by weightof C16/C18 sorbitan esters, 18% by weight of C16/C18 isosorbide esters,<1% by weight of C16/C18 sorbitol esters, and 3% by weight of polyol.

(ii) Preparation of Sorbitol Ester Component

(a) 330 g lauric acid, 390 g 70% aqueous sorbitol and 16 g of potassiumcarbonate were charged to a 1 liter flask, fitted with a stirrer,side-arm distillation, vacuum supply, thermocouple, nitrogen sparge anda thermostatted electric mantle. The reaction mixture was heated withstirring under vacuum to about 180° C. and water was distilled off. Thereaction was continued until the acid value was less than 5 mg KOH·g⁻¹.The product was then cooled and discharged.

The product was analysed as described herein and comprised 7% by weightof C12 sorbitan esters, 68% by weight of C12 sorbitol esters, and 25% byweight of polyol.

(b) 140 g methyl laurate, 99 g anhydrous sorbitol and 6 g of potassiumcarbonate were charged to a 500 ml flask, fitted with a stirrer,side-arm distillation, vacuum supply, thermocouple and nitrogen spargein an oil bath. The reaction mixture was heated with stirring undervacuum to about 160° C. and methanol was distilled off. The reaction wasmaintained at 160° C. under vacuum for about 3-4 hrs until a clear,single phase product was formed. Following a further 1 hour, the vacuumwas released, the oil bath switched off and the product discharged.

The product was analysed as described herein and comprised 2% by weightof C12 sorbitan esters, 73% by weight of C12 sorbitol esters, and 25% byweight of polyol.

(c) The procedure of (ii)(b) above was repeated except that a nitrogensparge without vacuum was employed. The product was analysed asdescribed herein and comprised 3% by weight of C12 sorbitan esters, 69%by weight of C12 sorbitol esters, and 28% by weight of polyol.

(d) The procedure of (ii)(b) above was repeated except that 156 g methylcocoate, 100 g anhydrous sorbitol and 5.7 g potassium carbonate wereused. The product was analysed as described herein and comprised 1% byweight of C12 sorbitan esters, 50% by weight of C12 sorbitol esters, and35% by weight of polyol.

(iii) Preparation of Sorbitan Ester and Sorbitol Ester Mixture

9 parts by weight of the sorbitan ester component produced above washeated to 80° C., and 1 part by weight of one of the sorbitol estercomponents produced above was added with stirring whilst maintaining thetemperature at 80° C. The blended mixture was dropped onto a coolsurface and removed as flake.

Example 2 Oil in Water Cooling Milk (Preservative Free)

% w/w A. ARLAMOL HD (trade mark, ex Uniqema) 3 ARLAMOL E (trade mark, exUniqema) 3 Avocado oil 5 Wheatgerm Oil 2 Florasun 90 5 Oxynex LM 0.05 B.Surfactant Composition (produced in Example 1(iii)) 3.5 Propylene Glycol2 PRICERINE 9091 (trade mark, ex Uniqema) 3 Water 53.3 Keltrol F 0.15 C.Carbopol ETD 2050 (3% w/w solution) 5 D. Ethanol 15Procedure1. Disperse the Keltrol in the water of phase B at room temperature.2. Add other ingredients of B when a homogenous gel has been obtained.3. Heat phase B to 80° C.4. Homogenize B with Ultra Turrax homogeniser for 30 seconds at 6,000rpm.5. Return to water bath for 30 minutes at 80° C.6. Heat phase A to 80° C.7. Add phase C to B while stirring at 800 rpm.8. Slowly add A to BC mixture while stirring at 800 rpm.9. Homogenize for 1 minute with Ultra Turrax at 10,000 rpm.10. Allow to cool to room temperature while stirring gently.11. Add phase D when the temperature is below 40° C.12. Neutralise with NaOH solution.

Example 3 Oil in Water Aqua Gel Cream

% w/w A. ESTOL 3603 (trade mark, ex Uniqema) 1.75 ESTOL 3609 (trademark, ex Uniqema) 1.75 ESTOL 1543 (trade mark, ex Uniqema) 1.75 ARLAMOLE (trade mark, ex Uniqema) 1.75 B. Surfactant Composition (produced inExample 1(iii)) 2 ATLAS G-2330 3 PRICERINE 9091 (trade mark, ex Uniqema)2.1 Water 81.5 Carbopol ETD 2050 0.2 C. Ethanol 3.5 Nipaguard BPX 0.7Procedure1. Disperse Carbopol in cold water of phase B while stirring moderately.2. Add other ingredients of B.3. Heat phase A to 80° C.4. Heat B to 80° C.5. Homogenize B with Ultra Turrax homogeniser when at 80° C., for 30seconds at 6,000 rpm.6. Return to warm water bath for 30 minutes at 80° C.7. Slowly add A to B while stirring at 800 rpm.8. Homogenize for 1 minute with Ultra Turrax at 10,000 rpm.9. Allow to cool to room temperature with gentle stirring.10. Add phase C when temperature is below 40° C.11. Neutralise with NaOH solution.

Example 4 Water in Oil in Water Sun Care Cream

% w/w A. ARLACEL 1690 (trade mark, ex Uniqema) 2.5 ARLAMOL HD (trademark, ex Uniqema) 2.5 ESTOL 3603 (trade mark, ex Uniqema) 7 TIOVEIL 50FCM (trade mark, ex Uniqema) 5 B. TIOVEIL AQ-G (trade mark, ex Uniqema)1.25 Germaben II 0.5 Water 31.25 C. Surfactant Composition (produced inExample 1(iii)) 5 Water 39.1 Keltrol F 0.4 TIOVEIL AQ-G (trade mark, exUniqema) 5 D. Germaben II 0.5Procedure1. Combine ingredients of phase A and heat to 80° C.2. Combine ingredients of phase B and heat to 80° C.3. Add B to A under Ultra Turrax homogeniser at 14,000 rpm andhomogenize for 5 minutes.4. Return the blend to 80° C.5. Disperse the Keltrol in the water of phase C at room temperature.6. Add Surfactant Composition when a homogenous gel is obtained.7. Heat the blend to 80° C.8. Homogenize with Ultra Turrax at 6000 rpm for 30 seconds.9. Return C to 80° C. for 30 minutes.10. Add the Tioveil to the heated C while stirring at 800 rpm.11. Add AB to C while stirring at 800 rpm.12. Homogenize with Ultra Turrax at 10000 rpm for 1 minute.13. Allow to cool to room temperature while stirring at 50 rpm.14. Add the Germaben when the temperature is below 40° C.15. Neutralise to pH 7 (approx) with citric acid solution.

Example 5 Oil in Water Moisturizing Cream

% w/w A. PRIPURE 3759 (trade mark, ex Uniqema) 5 ESTOL 3609 (trade mark,ex Uniqema) 5 ESTOL 3603 (trade mark, ex Uniqema) 5 MONASIL PCA (trademark, ex Uniqema) 2 Sweet Almond Oil 2 Lanette 22 2 Oxynex LM 0.05 B.Surfactant Composition (produced in Example 1(iii)) 5.5 Keltrol F 0.1PRICERINE 9091 (trade mark, ex Uniqema) 4 Water 68.65 C. Nipaguard BPX0.7Procedure1. Disperse the Keltrol in the water of phase B at room temperature.2. Add other ingredients of B when a homogenous gel has been obtained.3. Heat B to 80° C.4. Homogenise B with Ultra Turrax homogeniser when at 80° C., for 30seconds at 6,000 rpm.5. Return to warm water bath for 30 minutes at 80° C.6. Heat phase A to 80° C.7. Slowly add A to B while stirring at 800 rpm.8. Homogenize for 1 minute with an Ultra Turrax at 10,000 rpm.9. Allow to cool to room temperature while stirring gently.10. Add the Nipaguard when the temperature is below 40° C.

Example 6 Water Free Emulsion

% w/w A. ARLAMOL HD (trade mark, ex Uniqema) 5 ARLAMOL E (trade mark, exUniqema) 1.2 Dow Corning 245 Fluid 2.8 Paraffin Light Oil 10 B.Surfactant Composition (produced in Example 1(iii)) 5.5 PRICERINE 9091(trade mark, ex Uniqema) 74.5 C. Germaben II 1Procedure1. Heat phase B to 80° C.2. Homogenise B at 6,000 rpm for 30 seconds.3. Return B to 80° C. for 30 minutes.4. Heat phase A to 80° C.5. Add A to B under stirring at 800 rpm.6. Homogenise with an Ultra Turrax homogeniser for 1 minute at 10,000rpm.7. Allow to cool to room temperature while stirring at 120 rpm.8. Add Germaben when the temperature is below 40° C.

Example 7 Silicone in Water Emulsion

% w/w A. Dow Corning 345 Fluid 40 B. Surfactant Composition (produced inExample 1(iii)) 5.5 PRICERINE 9091 (trade mark, ex Uniqema) 4 Water 49.7C. Keltrol F 0.1 D. Nipaguard BPX 0.7Procedure1. Disperse the Keltrol in the water at room temperature.2. Add the remaining ingredients of phase B when a homogeneous gel isobtained.3. Heat the blend B to 80° C.4. Homogenise B at 6,000 rpm for 30 seconds.5. Return B to a warm water bath at 80° C. for 30 minutes.6. Heat phase A to 80° C.7. Add A to B under stirring at 800 rpm.8. Homogenise with an Ultra Turrax homogeniser for 1 minute at 10,000rpm.9. Allow to cool to room temperature while stirring at 120 rpm.10. Add the Nipaguard when the temperature is below 40° C.

Example 8 Oil in Water Aqua Gel Sunscreen Cream

% w/w A. Dow Corning 245 Fluid 4 ESTOL 1543 (trade mark, ex Uniqema) 4Dow Corning 200-100 c.St 2 PRISORINE 2021 (trade mark, ex Uniqema) 5MONASIL PCA (trade mark, ex Uniqema) 1.5 B. SOLAVEIL CT-200 (trade mark,ex Uniqema) 15 C. Surfactant Composition (produced in Example 1(iii)) 5Carbopol Ultrez 10 0.2 Veegum Ultra 0.8 MONAMATE RMEA 40 (trade mark, exUniqema) 0.2 Propylene glycol 4 Water 57.7 D. Sodium Hydroxide (30% w/wsolution) q.s. E. Fragrance 0.3 Liquid Germall Plus 0.3Procedure1. Disperse Carbopol in water. When fully dispersed add in Veegum Ultraand disperse again.2. Add the rest of ingredients of phase C and heat to 80° C.3. When C has reached 80° C., homogenise for 30 seconds and continue toheat at 80° C. for another 20 minutes.4. Combine all ingredients of phase A and heat to 75-80° C.5. Add phase B into A with high sheer mixing while maintaining thetemperature at 75-80° C.6. Add A/B mixture into C with high sheer mixing and homogenise at10,000 rpm for 1 minute.7. Adjust pH to 6.5-7.0 with sodium hydroxide.8. Continue to cool down to room temperature with stirring.

The resultant opaque cream showed no visible separation after 3 monthsstorage at 5° C., ambient temperature (23° C.), and at 40° C. The creamshowed no visible separation after 1 month at 50° C.

The invention claimed is:
 1. A liquid-crystal forming surfactant composition comprising: a) a sorbitan ester component comprising at least one sorbitan fatty acid ester; and b) a sorbitol ester component comprising at least one sorbitol fatty acid ester; wherein: i) the fatty acid residue of the at least one sorbitan fatty acid ester has a greater mean number of carbon atoms than that of the fatty acid residue of the at least one sorbitol fatty acid ester; ii) the fatty acid residue of the at least one sorbitan fatty acid ester and the fatty acid residue of the at least one sorbitol fatty acid ester have a saturated fatty acid content of greater than 80% by weight; and iii) the surfactant composition forms liquid crystals in water.
 2. The composition of claim 1, wherein the mean number of carbon atoms of the fatty acid residue of the at least one sorbitan fatty acid ester is at least 2 carbon atoms greater than that of the fatty acid residue of the at least one sorbitol fatty acid ester.
 3. The composition of claim 1, wherein the mean number of carbon atoms of the fatty acid residue of the at least one sorbitan fatty acid ester is 3 to 7 carbon atoms greater than that of the fatty acid residue of the at least one sorbitol fatty acid ester.
 4. The composition of claim 1, wherein the mean number of carbon atoms of the fatty acid residue of the at least one sorbitan fatty acid ester is 15 to 19 and/or the mean number of carbon atoms of the fatty acid residue of the at least one sorbitol fatty acid ester is 11 to
 14. 5. The composition of claim 1, wherein the ratio of sorbitan fatty acid esters to sorbitol fatty acid esters is 4 to 20:1 by weight.
 6. The composition of claim 1, wherein the composition comprises: a) 45 to 90% by weight of the at least one sorbitan fatty acid ester; b) 3 to 15% by weight of the at least one sorbitol fatty acid ester; and/or c) 7 to 25% by weight of isosorbide fatty acid esters.
 7. The composition of claim 1, wherein the sorbitan ester component comprises sorbitan palmitate and/or sorbitan stearate and the sorbitol ester component comprises sorbitol laurate.
 8. The composition of claim 7, wherein the composition comprises 2 to 15% by weight of the sorbitol laurate.
 9. The composition of claim 7, wherein the sorbitol laurate comprises at least 70% by weight of the sorbitol ester component.
 10. The composition of claim 1, wherein the sorbitol ester component comprises: a) at least 60% of sorbitol fatty acid monoesters; and b) less than 40% by weight of sorbitol fatty acid diesters.
 11. The composition of claim 1, wherein the composition comprises 2 to 15% by weight of polyol.
 12. The composition of claim 11, wherein 30 to 80% by weight of the polyol is sorbitol.
 13. A method of forming the liquid-crystal forming surfactant composition of claim 1, comprising mixing together the sorbitan ester component and the sorbitol ester component.
 14. The method of claim 13, wherein the sorbitan ester component comprises 65 to 85% by weight of the at least one sorbitan fatty acid ester.
 15. The method of claim 13, wherein the sorbitol ester component comprises 50 to 85% by weight of the at least one sorbitol fatty acid ester.
 16. An emulsion comprising the liquid-crystal forming surfactant composition of claim
 1. 17. The emulsion of claim 16, wherein the emulsion comprises 1 to 7% by weight of the liquid-crystal forming surfactant composition.
 18. The emulsion of claim 16, comprising liquid crystals which are stable for greater than 3 months at ambient temperature, and/or greater than 2 months at 40° C., and/or greater than 1 month at 50° C.
 19. The emulsion of claim 16, wherein the emulsion is stable for greater than 4 months at ambient temperature, and/or greater than 3 months at 40° C., and/or greater than 2 months at 50° C.
 20. A personal care or cosmetic product comprising the liquid-crystal forming surfactant composition of claim
 1. 21. A method of using the liquid-crystal forming surfactant composition of claim 1 to stabilize an emulsion, comprising mixing said liquid-crystal forming surfactant composition with the emulsion.
 22. The method of claim 21, wherein the liquid-crystal forming surfactant composition: a) comprises at least 3% by weight of the at least one sorbitol fatty acid ester; b) stabilizes an oil in water emulsion; and c) forms liquid crystals in the water phase of the oil in water emulsion. 